1. Field of the Invention
The invention relates to special-purpose electric motors used for driving various work-performing members through angular oscillations, and more particularly it relates to electromagnetic oscillation motors.
2. Description of the Prior Art
There is known an electromagnetic oscillation motor (see SU Inventor's Certificate No. 1,040,573; Int. Cl..sup.3 HO2K 33/14, dated 1983) having a stator with a winding received on two pairs of poles symmetrically arranged in a circle, the parallel paths of this winding being connected to a voltage source through respective rectifiers connected in opposition to each other, and a salient asymmetrically armature whose poles are offset in pairs in opposite directions relative to the symmetry axis by one half of their angular width.
In this known motor, the incorporation of the rectifiers has been found to affect the power characteristics of the motor, while the asymmetry of its armature, the small spacing of the adjacent poles in particular, has been found to incur manufacturing difficulties in application of the bias winding onto the armature, and to impair the cooling conditions. Furthermore, in motors of higher power ratings the asymmetry of the armature adversely affects the dynamic characteristics of the motor.
There is also known an electromagnetic oscillation motor (see FR Pat. No. 1,552,754; Int. Cl. HO2K, published on Jan. 1, 1969) comprising a four-pole symmetrical armature and an asymmetrical four-pole stator whose poles are offset in the same direction through one half of the angular width of the poles. The a.c. winding of the stator includes two paths connected in parallel and received on the opposite poles of the stator. Each path has two serially connected coils and is connected to a power supply source through a semiconductor diode. During odd half-cycles, the alternating current of the power supply source is directed through one parallel path of the stator winding, and during even half-cycles it is directed through another path. Consequently, corresponding magnetic fluxes are excited by the two paths of the magnetic circuit, generating sign-variable driving torque resulting in oscillations of the armature in accordance with the harmonic law.
However, the incorporation of the half-wave rectifiers in this known structure of an electromagnetic oscillation motor impairs its power characteristics and distorts the current curve, thus adversely affecting the power supply source. Moreover, this structure prohibits full compensation for the electromotive force of self-induction by using bias circuits, on account of the parallel paths of the stator winding being arranged on the opposite poles, which involves intersection of the magnetic fluxes developing the driving effort. The extended length of the magnetic circuit further impairs the power characteristics of the oscillator motor.